However+,

[wpqin]

Dear RonBee:

I review our former discussions on my manuscript today and learn more from your corrections. However, something still puzzles me. For example, the however in the following sentence, must we use a comma after the however? Why?
Thanks in advance!

First, we shut off the IR laser and struck the solid sample surface with one or a few laser pulses, and then as soon as possible, we opened the IR laser; however, no scattered light could be observed.

[RonBee]

Dear RonBee:

I review our former discussions on my manuscript today and learn more from your corrections. However, something still puzzles me. For example, the however in the following sentence, must we use a comma after the however? Why?
Thanks in advance!

First, we shut off the IR laser and struck the solid sample surface with one or a few laser pulses, and then as soon as possible, we opened the IR laser; however, no scattered light could be observed.

Yes, you need a comma after however there. The simplest explanation for that would be that in speech there would be a pause after however. The other explanation that comes to mind (and it isn't much of one) is that however functions like nevertheless, and nevertheless takes a comma after it. Perhaps something additional (and more useful) will occur to me.

8)

[Tdol]

As 'however' connects two sentences, it has commas around it to separate it from the sentence it occurs in.

[RonBee]

As 'however' connects two sentences, it has commas around it to separate it from the sentence it occurs in.

Wouldn't that make it a conjunction? I see using "however" at the beginning of a clause but not as a conjunction.

8)

[Tdol]

It's a conjunct.

[wpqin]

Thank you, my teachers. I have gotten some about that.

[RonBee]

So it's a conjunct and not a conjunction. (Thanks for the link.)

8)